JPH11142348A - Meandering follow-up device for defect inspecting device and defect inspecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the highly accurate detection of a defect over a plurality of regions, by storing both threshold values for detecting bright and dark defects with values corresponding to each region with threshold boundary coordinates as a boundary in threshold value memory. SOLUTION: First, a CCD camera 1 reads the image of an object to be inspected at the read location of the Camera 1. Its analog signal is converted into digital data by an A/D converter 3, and multi-valued image data is stored in reference value memory 6 as a line of data and is used as reference data. Next, a CPU 10 detects the output value of the A/D converter 3, and the edge coordinates of a boundary is stored in RAM 9. Next, by the output of a comparator 4, threshold values for detecting bright and dark defects are stored in threshold value memory 7A. Then threshold values for detecting bright and dark defects are stored in threshold value memory 7B in a similar way. During this time, the threshold values in the memory 7A and the output of the A/D comparator 3 are compared by the comparator 4 to detect the presence or absence of a defect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a meandering tracking device for a defect inspection apparatus for an inspection object having a plurality of regions having different transmittances or reflectances using a line image sensor. Examples of the inspection object include a continuous metal sheet, a film, a nonwoven fabric, and a vapor-deposited film.

[0002]

2. Description of the Related Art As a meandering follow-up method in a conventional defect inspection apparatus, one disclosed in Japanese Patent Application Laid-Open No. 8-145908 is known. In this conventional technique, when the inspection object meanders, an edge position of the inspection object is detected, a deviation from a reference edge position detected in a state where the inspection object does not meander is determined in advance, and based on the determined deviation amount. It is disclosed to correct the position of the inspection window.

[0003]

In the above prior art, a case of an inspection object having a plurality of regions having different light transmittances or reflectances in the width direction, for example, a case of a vapor deposition film vapor-deposited in a stripe shape is considered. I haven't. Therefore, since the boundary between the inspection areas cannot be recognized as an edge, there is a problem that a change in the reflectance or the transmittance at the boundary is easily mistaken for a defect.

[0004] It is an object of the present invention to provide a defect inspection capable of performing a defect inspection with high accuracy even in the case of an inspection object having a plurality of regions having different light transmittances or reflectivities in the width direction. It is an object of the present invention to provide a meandering tracking device and a defect inspection device.

[0005]

In order to achieve the above object, according to the present invention, after detecting an edge at a boundary between a plurality of regions, a threshold boundary coordinate of an inspection region is corrected by image processing in the vicinity of the edge. Like that. That is, according to the invention, when one side of the edge coordinate is a non-inspection area and the other side is an inspection area, the threshold coordinate is set at a position where the edge coordinate is shifted by a predetermined amount toward the inspection area. If both sides of the boundary are inspection areas, the dark defect detection threshold is shifted by a predetermined amount to the side of the area that outputs a lower value among the outputs of the line image sensor for the bright defect detection threshold. For the threshold, a threshold boundary coordinate setting means for setting the threshold boundary coordinates at a position where the edge coordinates are shifted by a predetermined amount to the side of the area outputting the high value of the output of the line image sensor, A meander tracking device for a defect inspection device, comprising: a threshold memory for storing at least one of a bright defect detection threshold and a dark defect detection threshold having a value corresponding to each area for each line. A.

[0006] The threshold memory may be provided with a threshold memory for further storing a threshold value for density detection for determining the density of a defect. According to the present invention, there is further provided a defect inspection apparatus comprising: the meandering tracking apparatus; and a binarization processing unit that binarizes image data of each line obtained from the line image sensor using a threshold value of a corresponding line. .

Since a threshold value suitable for each of a plurality of regions is set, highly accurate defect detection can be realized in each region. Further, since the threshold boundary coordinates are shifted from the edge coordinates by a predetermined amount in consideration of the meander amount for each inspection position, even if the inspection area of the inspection object is meandering, the defect inspection can be performed by following the meandering. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a meandering follow-up device for a defect inspection device according to an embodiment of the present invention will be described in detail. FIG. 1 is a block diagram showing a meandering tracking device for a defect inspection device according to an embodiment of the present invention. In the figure, 1 is a line CCD camera used as a line image sensor, 2 is an image processing device, and 12 is a host computer. The image processing device 2 is alternately used for writing and reading of the A / D converter 3, the comparator 4, the run length encoding circuit 5, the reference value memory 6, and the bright defect detection threshold and the dark defect detection threshold. A first threshold memory 7A and a second threshold memory 7B, and a first run-length buffer 8A and a second run-length buffer 8B having a capacity of, for example, 64 KB.
, A random access memory (RAM) 9, a central processing unit (CPU) 10, and a general-purpose interface (GP-
IB) and the like. In the embodiment of the present invention described below,
Since the threshold memory stores both the light defect detection threshold and the dark defect detection threshold, the light defect and the dark defect are detected by performing the binarization processing using each of these two. Can be. However, when it is not necessary to detect both a bright defect and a dark defect, either one of the threshold for detecting a bright defect or the threshold for detecting a dark defect may be used according to the feature of the defect.

As the line CCD camera 1, for example,
There is an SCD type line CCD camera manufactured by Mitsubishi Rayon Co., Ltd. The number of elements of this line CCD camera is 1024-
5000, a driving frequency of 20 MHz, and a scanning cycle of 0.1 ms at the maximum. The line CCD camera selects an appropriate model depending on the inspection object. The pixel arrangement is not particularly limited, either, and is appropriately determined depending on the inspection mode, the object, and the like. The RAM 9, the CPU 10, the first threshold memory 7A, and the second threshold memory 7B constitute edge detecting means and threshold boundary coordinate setting means. In the present embodiment, since two threshold memories, the first threshold memory 7A and the second threshold memory 7B, are used, while the threshold is being written in one threshold memory, it has already been written in the other threshold memory. Writing and reading can be performed alternately by using the threshold value for inspection of the inspection object. The first threshold memory 7A and the second threshold memory 7B may store a threshold for detecting the density of a defect in addition to the threshold for detecting a bright defect and the threshold for detecting a dark defect.

Next, the operation of the apparatus shown in FIG. 1 will be described with reference to FIGS. FIG. 2 is a flowchart showing a processing procedure in the apparatus of FIG. As shown in FIG. 2, the present embodiment has four steps from step S1 to step S4. Hereinafter, a series of processes from step S1 to step S4 will be collectively referred to as “one cycle” as appropriate. FIG.
FIG. 2 is a diagram for explaining a first embodiment of the present invention in the device shown in FIG. 1.

[0011] As shown in FIG.
The field of view of the camera 1 is set to a range wider than (the width of the inspection area A and the inspection area B + the maximum amount of meandering) in consideration of the meandering of the inspection target. FIG. 3B shows a reading position of the line CCD camera 1 on a sheet 30 having different light transmittance or reflectance in the width direction as an example of the inspection object. In addition, the vertical arrow in the figure is the traveling direction. The periphery of the sheet 30 indicated by oblique lines is the background, and the reflectance or transmittance is low. Hereinafter, the background is referred to as a “non-inspection area”. In the embodiment of the present invention, a configuration is adopted in which reflected light from a light source (not shown) is received by a line CCD camera. Therefore, in the following description, only the reflectivity will be appropriately described, but a configuration in which transmitted light from the light source is received will be described. Can be similarly applied to the transmittance in the case of taking.

The portion sandwiched between the hatched portions is an inspection region which is a deposition portion. The inspection area is divided in the width direction into an inspection area A having a low reflectance and an inspection area B having a high reflectance. Further, it is assumed that there is a bright defect a and a dark defect a at the reading position of the line CCD camera 1, and these defects are detected by the apparatus of the present invention. Since the change in reflectance or transmittance is large at the boundary between the inspection areas, if the inspection area is meandering as shown in the running direction of the inspection object, the normal part is likely to be mistaken as a defect. Therefore, in the embodiment of the present invention, as will be described in detail later, the threshold boundary coordinates at each boundary between the inspection region and the inspection region or the non-inspection region are appropriately shifted to improve the resistance to meandering.

In FIG. 2, first, in step S1, reference data is set. The line CCD camera 1 reads an image at one reading position (see FIG. 3B) of the line CCD camera 1 of the inspection object. The inspection object is
The inspection position is moved by a moving device (not shown) so that the inspection position moves in the traveling direction. It is also possible to move the line CCD camera instead of moving the inspection object. An analog signal obtained by imaging is converted to A /
The data is converted into digital data of, for example, 8 bits per pixel by the D converter 3 to obtain multi-valued image data.
The multilevel image data is recorded in the reference memory 6 as data for one line, and is used as reference data. Since there is a possibility that the inspection object used for obtaining the reference data may also contain a defective portion, the image data obtained by scanning a plurality of lines at the above reading position is obtained for each pixel. The influence of a defect may be reduced by averaging a plurality of values obtained.

The reference data thus determined is used for determining a threshold in step S4. Next, in step S2, based on the reference data set in step S1, coordinates of an edge which is a boundary between a plurality of regions of the image of the inspection object are detected. This is performed by detecting a change point of the output value of the A / D converter 3, and FIG.
(C), the edge coordinate of the boundary between the non-inspection area and the inspection area A is E ₁ , the edge coordinate of the boundary between the inspection area A and the inspection area B is E ₂ , and the inspection area B and the non-inspection area boundary edge coordinates of the are E _3. The edge coordinates of this boundary are detected by the CPU 10 and stored in the RAM 9.

The edge coordinates of each area of the inspection object are RA
It is detected based on the digitized image data stored in the reference value memory 6 by the M9 and the CPU 10.
There are two types of edge detection means. That is, one is a case where the position where the image data changes from the top to the bottom of the preset value or from the bottom to the top of the value is set as the edge, and the other is the case where the image data of the pixel at a predetermined distance is set as the edge. This is a case where detection is performed based on a difference between the two. Which one to adopt is selected depending on the state of the edge portion to be inspected.

The former has the advantage that the edge position can be accurately detected even if the background and the output level of the inspection object are stable, even if the image is slightly blurred. The latter has the advantage that if the change in the output level at the edge portion is large to some extent, the proper position can be detected even if there are a plurality of types of output levels of the inspection target. When detecting an edge, the reference data corresponding to the pixels of the line CCD camera is checked in either an ascending order (from left to right) or a descending order (from right to left). In the case of detecting an edge that is a boundary between the background of the inspection object and the inspection area, the output of the background is often more stable than the output of the inspection area. Do it. Therefore,
Edge detection, which is the boundary between the leftmost non-inspection area and the inspection area on the right side of the inspection object, is performed in ascending order, and is the boundary between the rightmost non-inspection area of the inspection object and the inspection area on the left side. Edge detection is performed in descending order.

In step S3, threshold boundary coordinates are set, and it is determined whether an area between the threshold boundary coordinates is an inspection area or a non-inspection area. In the present embodiment, the non-inspection area is a portion corresponding to the background shown in FIG. 3B, and is a portion having the lowest reflectance or transmittance. Step S2
When the edge coordinates calculated in are used as a reference, FIG.
In this example, the range of the coordinate range and E ₃ ~ field right end of the 0 to E ₁ is a non-inspection area, E ₁ to E ₂ inspection regions A,
E _{2 to} E ₃ are inspection areas B. Edge coordinates between these areas are also stored in the RAM 9.

Between the non-inspection area and the inspection area, the threshold boundary coordinates are shifted toward the inspection area by a predetermined amount. Between the inspection areas, threshold boundary coordinates are set at positions shifted from the edge coordinates by a predetermined amount on the inspection area side having a low reflectance or transmittance in the case of detecting a bright defect, and the reflectance or transmission is detected in the case of detecting a dark defect. A threshold boundary coordinate is set at a position shifted from the edge coordinates by a predetermined amount toward the inspection area having a high rate.

The predetermined amount is determined according to the amount of meandering of the inspection object. The predetermined amount is preferably set so as to be larger than the maximum value of the meandering amount of the inspection object during one cycle, and more preferably set to a value that is several pixels larger than the maximum value of the meandering amount. In other words, the edge coordinates between the inspection areas are shifted by a predetermined amount toward the area that outputs a higher value among the outputs of the line image sensor for the bright defect detection threshold, and the line image sensor is used for the dark defect detection threshold. Are shifted by a predetermined amount to the side of the area for outputting a low value among the outputs of the above. This prevents erroneous detection near the edge even if the inspection area of the inspection object meanders.

The shift of the boundary coordinates will be specifically described with reference to the drawings. Regarding the threshold boundary coordinates for bright defect detection, the threshold boundary coordinates E ′ ₁ and E ′ between the non-inspection area and the inspection area
₃ respectively, in the line edge coordinates E ₁ and E ₃ than was c pixel shifted to the inside position of the CCD camera 1 of the output waveform, namely E _'1 = E ₁ + c and E' ₃ = E ₃ -c . The same applies to the threshold boundary coordinates E ″ ₁ and E ″ ₃ for dark defect detection, that is, E ″ ₁ = E ₁ + C and E ″ ₃ = E ₃ −c. The boundary between the inspection area A and the inspection area B is set to E ′ ₂ = E ₂ −c so that the boundary is not mistaken for a defect. here,
c is a numerical value determined in consideration of the meandering degree of the inspection area.

When using the dark defect detection threshold boundary coordinates,
Regarding the boundary between the inspection area A and the inspection area B,
E ″ ₂ = E ₂ + c so as not to mistake the boundary as a defect
And Next, it is determined what area is between the threshold boundary coordinates determined in this way. For example, RAM9
The order in which the regions are lined up is stored, and for example, it is determined in order from the left whether each region is an inspection region or a non-inspection region.

In step S4, for example, a threshold value stored in the threshold value memory 7A is set. The bright defect detection threshold is set such that the output of the comparator 4 for a region having an output level larger than the threshold becomes “1” in the case of the bright defect detection. The dark defect detection threshold is set such that the output from the comparator 4 for a region having an output level lower than the threshold becomes “1” in the case of dark defect detection. Based on the reference data set in step S1, the reference data for each pixel and the ratio set in advance for each inspection area, for example, 150 for the bright defect inspection area A
%, And 50% in the dark defect inspection area B,
This product is stored as a new threshold. This calculation is performed by a threshold determination program stored in the RAM 9 based on the reference data of each pixel, and when a new threshold is determined, the new threshold is stored in, for example, the first threshold memory 7A. As the threshold, a predetermined fixed value may be adopted for each inspection area.
Further, the threshold value differs between the non-inspection area, the inspection area A, and the inspection area B.

The threshold value of the non-inspection area is a threshold value for detecting no image data, and is set to 255 in the case of detecting a bright defect and to 0 in the case of detecting a dark defect.
After the dark defect detection threshold and the light defect detection threshold are stored in the first threshold memory 7A in this manner, step S is performed again.
Returning to 1, the same threshold value is set for the next line for which the threshold value is to be set, and stored in the second threshold value memory 7B.
During this time, the threshold of the first threshold memory 7A and the output of the A / D converter 3 are compared by the comparator 4 to detect the presence or absence of a defect.

In the next cycle, the process returns to step S1 again, sets the threshold value through the steps up to step S4, overwrites the first threshold value memory 7A, and stores the data in the second threshold value memory 7B during that time. The presence or absence of a defect is detected using a threshold. Each of the threshold memories 7A and 7B is a memory of 8 bits / pixel. When there is only one threshold memory, the fetched multivalued image data must be used as data for setting a threshold and performing defect inspection in one cycle. However, in this case, it is necessary to wait until the setting of the threshold is completed every time one line is inspected.
Quick inspection cannot be performed. In the present embodiment, continuous and rapid inspection can be performed by alternately performing the operation of performing the binarization processing in the other memory while writing the threshold value in one memory as described above. . When two threshold memories are used, the threshold corresponding to the image data of each line is written to the threshold memory in the cycle in which reading is performed, and is read in the next cycle. Therefore, when binarizing the image data of each line, a threshold value read out in the next cycle is used.
In addition, it is not necessarily one for each scan of the line CCD camera.
Instead of performing a cycle step, one cycle step may be performed for several scans.

FIG. 3D shows data obtained by comparing the output of the A / D converter 3 with the threshold value for the bright defect detection of the threshold value memory 7A read out in the next cycle by the comparator 4. Since the output value of the A / D converter 3 corresponding to the bright defect A is larger than the threshold value stored in the threshold memory 7A, the output of the comparator 4 becomes "1" level.
Is at the "0" level. In the next cycle,
A new bright defect detection threshold is stored in the threshold memory 7B.

FIG. 3E shows data obtained by comparing the output of the A / D converter 3 with the dark defect detection threshold of the threshold memory 7A, which is also read in the next cycle, by the comparator 4. . A / D corresponding to dark defect a
Since the output value of converter 3 is smaller than the threshold value stored in threshold value memory 7A, the output of comparator 4 is at "1" level, and the output of comparator 4 is at "0" level in the inspection area other than dark defect A. . In the next cycle, a new dark defect detection threshold is stored in the threshold memory 7B.

The digital data output from the A / D converter 3 is compared with the threshold stored in the first threshold memory 7A or the second threshold memory 7B in the comparator 4 for each element of the line CCD camera 1. Are output from the comparator 4 as binarized data. Since the threshold value is determined on a pixel-by-pixel basis, the comparator 4 can binarize an output signal for each element, which absorbs variations between elements of the line CCD camera 1, illumination unevenness, and lens distortion.

The binary data output from the comparator 4 is a run-length encoding circuit 5 for obtaining a transition point address from "0" to "1" or from "1" to "0".
, And is stored in the first and second run-length buffers 8A and 8B. The run-length codes stored in the run-length buffers 8A and 8B are alternately subjected to connectivity processing by the CPU 10. Here, the connectivity processing refers to processing while comparing data in a plurality of continuous scan lines between the lines. By performing this connectivity processing, it is possible to recognize the defect of the inspection object and measure the morphological feature.

Data such as inspection conditions and inspection results are transferred to a host computer 12 via an input / output interface (I / O) 11. In the host computer 12, inspection conditions are set and inspection results are displayed.
In the threshold memories 7A and 7B, in addition to the above-described bright defect detection threshold and dark defect detection threshold, as shown in FIG. A dark defect density detection threshold for determining the density in dark defect detection may be stored.

Note that the density detection threshold value is a defect detection threshold value.
Set to a larger or smaller value. For example, bright defects
When detecting a dark defect (bright defect)
Is larger than the light defect detection threshold
Use a good value. FIG. 4 illustrates a second embodiment of the present invention.
FIG. FIG. 4A shows the inspection object and the line.
Indicates the reading position of the CCD camera. As inspection object
Indicates that a plurality of deposition areas, which are inspection areas, alternately
Area A where the reflectance is low₁And A_TwoAnd high reflectivity
Area B₁And B_TwoAnd steam
An example of a deposition film is shown. Line CCD camera 1
The field of view of FIG.
(Inspection area A₁, B₁, A _TwoAnd B_TwoTotal width of
(The maximum meandering amount). Also,
The reading position of the CCD camera 1 is inspected as shown in the figure.
Position R parallel to the width direction of the object_AAnd R_BIt is.

FIG. 4B shows a line CCD for one line when the image is read at the reading position _RA in FIG. 4A.
The figure shows a digital signal waveform obtained by converting the output of the camera 1 by the A / D converter 4 and a threshold stored in the threshold memory 7A or 7B. As shown, line C
The output of the CD camera 1 is the output from the inspection area A ₁ (or A ₂ ) <the output from the non-inspection area <the inspection area B ₁ (or B
₂ ) output from

As in the first embodiment, the first threshold memory 7A and the second threshold memory 7B are used alternately for threshold storage and threshold read. Edge coordinates of the boundary between the non-inspection area and the inspection area A ₁ is E _1, the inspection region A ₁ and B ₁
Edge coordinates of the boundary between is E _2, the inspection region B ₁ and A
Edge coordinates of the _second boundary is E _3, the inspection region A ₂ and B
Edge coordinates of the _second boundary is E _4, the edge coordinates of the inspection area B ₂ boundary of the non-inspection area is E _5.

The threshold boundary coordinates are E 'as shown in the figure.₁~ E '
_FourAnd the edge coordinates E₁~ E _FourShifted from
And threshold boundary coordinates stored in the second threshold memory 7B
E ″ as shown₁~ E ''_FourIt is an edge
Coordinate E₁~ E_FourHas been shifted from Edge coordinates
The method of calculating the threshold boundary coordinates from is described in the first embodiment.
This is the same as the method described above.

FIG. 4C shows a line C shown in FIG.
1 when read by the reading position R _B of the CD camera 1
The waveform of the line CCD camera 1 for the row and the threshold memory 7A
Or, the threshold stored in 7B is shown. FIG. 4 (a)
R _B reading position of the line CCD camera 1 from R _A
Or the width of the inspection area fluctuates,
The edge coordinates of the threshold memories 7A and 7B are changed.

Also in the case of FIG. 4, a threshold value for detecting a light defect density and a threshold value for detecting a dark defect density may be employed similarly to FIG.

[0036]

As described above, according to the meandering tracking device for a defect inspection device of the present invention, the inspection object is divided into a plurality of inspection regions in the width direction, and the plurality of inspection regions have different reflectances or transmittances. , It is possible to adjust the inspection range by automatically following the meandering of the inspection object. Further, even if the widths of the plurality of inspection areas change, the inspection range can be adjusted by automatically following the inspection area. The defect inspection apparatus according to the present invention can perform a highly accurate defect inspection even for the above-described inspection target.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a meandering tracking device for a defect inspection device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure in the apparatus shown in FIG.

FIG. 3 is a diagram for explaining a first embodiment of the present invention in the device shown in FIG. 1;

FIG. 4 is a diagram for explaining a second embodiment of the present invention in the device shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Line CCD camera 2 ... Image processing apparatus 3 ... A / D converter 4 ... Comparator 5 ... Run length encoding circuit 6 ... Reference value memory 7A ... 1st threshold memory 7B ... 2nd threshold memory 8A ... 1st run length buffer 8B: second run length buffer 9: RAM 10: CPU 11: I / O interface 12: host computer

Claims (3)

[Claims] 1. A line image sensor for obtaining image data for each line in a width direction of an inspection target having a plurality of inspection regions having different light transmittances or reflectances in a width direction, and an inspection target of the line image sensor. A moving device that changes the relative positional relationship between the inspection object and the line image sensor so that the inspection range above moves in the traveling direction of the inspection object; and a digital image signal of the output signal of the line image sensor. Edge detection means for detecting edge coordinates indicating a boundary between adjacent areas of the plurality of inspection areas; and, if one side of the edge coordinates is a non-inspection area and the other side is an inspection area, the edge coordinates are used as the inspection area. The threshold boundary coordinates are set at a position shifted by a predetermined amount to the side of, and when both sides of the boundary are inspection areas, the threshold for bright defect detection is set. Outputs a higher value among the outputs of the line image sensor as to the dark defect detection threshold at a position where the edge coordinates are shifted by a predetermined amount to the side of the area outputting the lower value among the outputs of the line image sensor. Threshold boundary coordinate setting means for setting threshold boundary coordinates at a position where the edge coordinates are shifted by a predetermined amount to the side of the region; a threshold for detecting a bright defect having a value corresponding to each region with the threshold boundary coordinates as a boundary; A meander following device for a defect inspection device, comprising: a threshold memory for storing at least one of the defect detection thresholds for each line. 2. The meandering follow-up device for a defect inspection device according to claim 1, further comprising a threshold value memory for further storing a density detection threshold value for determining the density of a defect, as said threshold value memory. 3. A meandering tracking device according to claim 1 or 2, further comprising: a binarization processing unit that binarizes image data of each line obtained from the line image sensor using a threshold value of a corresponding line. Equipped defect inspection equipment.